1. Field of the Invention
The present invention relates to aligning a driver to a pump and, in particular, to an alignment assembly, method, and system for aligning a motor to a pump that significantly increases the life of the pump by improving accuracy of motor shaft to pump shaft alignment, and further enhancing the safety of an alignment crew.
2. Description of Related Art
Aligning a driver (e.g., a motor) to a pump is an onerous, dangerous, time-consuming, and challenging task. To achieve proper alignment, exacting alignment between the centerline of a motor and the centerline of a pump is a must. A slight misalignment of the coupling of the motor and pump can result in a significant misalignment deep within the pump, which can cause many problems, such as reduced pump life, loss of derived income due to pump failure, and potential dangerous/fatal pump conditions. Further, misalignment between the motor and pump can cause other problems, including, but not limited to: extreme heat generated between a motor coupling and a pump coupling; severe wear in gear couplings; cracked or failed shafts caused by constant flexing; overload on bearings resulting from overheating and fatigue problems; as well as excessive radial/angular movement of rotating design seals.
Unfortunately, many pumps are never properly aligned with their driver, so misalignment and the attendant problems are common. This misalignment can be attributed to rushed alignment procedures so as to reduce the amount downtime of the pump, and/or because of faulty alignment methods/tools.
Conventional alignment solutions used include: (i) a reverse indicator alignment, (ii) a laser alignment, and (iii) a C or D frame adapter. The reverse indicator method is typically performed in only three stages. The first stage includes determining where the components are located in relationship to each other. The next stage includes calculating what components are to be moved and how far, whereby aligning the centerline of the driver with the centerline of the pump. And a last step is moving the hardware, normally the motor, into the desired position. This approach, obviously, can take an excessive amount of time due to the constant shifting/moving that may be required.
The laser alignment method performs similarly to the reverse indicator method, but instead of using analog or digital equipment to calculate the relationship between the motor and the pump, this alignment method uses laser equipment. By using the laser equipment, one is able to obtain precise measurements and, rather quickly, calculate the amount of movement between the components that are necessary. The components, or hardware, must still be moved, which is ordinarily the most difficult and time-consuming step of alignment.
Either a C frame adapter or a D frame adapter can be used to align a motor to a pump. Commonly, the C or D frame adaptors are useful for smaller sized jobs, and are not suitable for larger motors and pumps, due to size constraints of a housing of the motor to the pump.
In large pumps, for example, large vertical condensate pumps used in power plants, shaft alignment can be an extremely challenging task. Commonly, in these large pumps, a pump shaft and an impeller are rigidly coupled to a vertical flange-mounted motor. Obtaining meaningful alignment measurements becomes near impossible with the rigid or solid coupling.
When the rigid coupling remains connected and tightened, alignment measurements can not be measured conventionally (i.e., by rotating both coupled shafts), because no relative movement between the shafts is permitted, as would be the case with, for example, a flexible coupling. Instead, the solid coupling makes a rigid connection between the shafts, resulting in severe deflection of the shafts should misalignment exist.
Angular misalignment between the centerlines of rotation, however, can be evidenced by excessive vibration and wear at a first guide bearing of the pump shaft. If the couplings are completely disconnected, the pump shaft settles on the bottom of a pump pit and may be impossible to turn, even if (as is occasionally done) the pump shaft rests on a specially fitted conical seat to assist in controlling pump shaft play at the bottom of the pit. One key concern is that the shimming corrections for angularity that are performed at the motor flange must not result in changing the radial position of the pump shaft. Most unnecessary axial adjustments for pump component clearances occur via an adjustment nut positioned at the top of the pump shaft, as shim work involving the motor can be counter-adjusted by the adjustment nut. Further, thrust bearings of the motor are designed to carry the weight of the pump shaft. The pump shaft can be lifted from the lowermost resting place when spacing is established upon installing coupling bolts to the motor and pump couplings. The coupling bolts are tightened, and thus the pump shaft is lifted a controlled distance, to be supported by the thrust bearing of the motor. Providing that the motor is properly aligned to pump, the pump shaft will hang freely via the motor coupling. Accordingly, no portion of the pump shaft, impeller, or wear rings touches any solid or metallic portion; indeed, when properly aligned, the pump shaft rotates without touching anything other than the pumpage media (liquid, fluid, and the like).
Traditionally, alignment is performed with dial indicators, either of the analog or digital variety. Alignment is a tedious process taking significant time, and thereby is very costly.
In relation to power plant pump systems, it would be beneficial to provide a method and tool that could enhance industrial safety for both personnel and equipment during pump alignment, and further speed up the process of alignment. Presently, alignment methods are performed manually by rotating the motor shaft. A dial indicator is attached to the motor coupling and “tracked” around the face and rim of the stuffing box. The high breakaway force required to start the motor shaft rotating creates a personnel hazard.
Once the motor starts rotating, one mechanic must maintain rotor movement, while another mechanic reads and obtains the dial indicators, allthewhile dodging the rigging, which an extremely hazardous condition. Due to the potential for injury and even some resulting fatalities, the manual rotation of vertical motors of large vertical pumps must be limited, if not eliminated.
For example, a large vertical pump may need to be rebuilt and repositioned, connecting it to inlet and discharge piping. When repositioned, the motor is placed in an approximate position on top of the pump. A crew of seasoned mechanics is often assigned the task of aligning the motor to the pump. The mechanics bolt a rotation device to the motor coupling, wherein the rotation device can act as a handle by which a force to the motor can be jump-started. Essentially, the motor can be turned manually while indicators are mounted, adjusted, and monitored. Typically, due to the force required to keep the motor shaft rotating, at least two members of the crew must constantly manually turn the motor.
The jump-start of rotating the motor involves placing the rotation device to the motor coupling in a position where one of the handles aims out an open window of a coupling cage. This enables a loop of a nylon strap or chain, and a come-along to be attached providing the initial burst of power to jump-start rotation. During the initial rotation of the motor, the nylon strap drops free, and before the motors coasts down, the crew must continue to rotate the motor manually.
It is inevitable that during manual rotation, uneven lateral pressure on the motor will be applied. A rim indicator will register wherever it happens to be at the instant of actual reading, but one can not know if its position represents a truly centered motor shaft or not. Thus, manual jump-starting of a pump should be limited, if not eliminated, to protect workers. This can be accomplished by properly aligning the motor to the pump without such a jump-start procedure.
Placement of a rotor of a motor into action requires a large amount of torque. For instance, with a heavy rotor, such as an exemplary 4,500 horsepower condensate pump motor (which can weigh in excess of 13,000 pounds), getting a film of oil between the rotor and a motor thrust bearing to support rotation requires application of a large amount of torque. Some vertical pump motors, e.g., a reactor coolant pump motor, have a lift pump arrangement that minimizes the amount of torque required to place the motor into motion. Indeed, some component drive assemblies have turning gears that rotate the assembly upon engagement.
While the amount of torque required for maintaining rotor rotation is less than initial break away torque, maintaining application of this force can be difficult, as well as dangerous. An enclosure where the force must be applied is restricted, and further limits tools that can be used to create this rotation. This enclosure also requires access to an individual performing the drive and driven component alignment process. Commonly, designs of motors fail to consider this limitation and implementation of a turning drive assembly feature would be costly and prohibitive to most existing designs. Moreover, maintenance of components is usually not included in a component design.
FIG. 1 illustrates the motor 105 in communication with the pump 110. The alignment process of conventional systems requires the rotation of the motor shaft 115 and the motor coupling 120. This rotation is illustrated in FIG. 1 with the arrow. Rotation of the motor shaft 115 and the motor coupling 120 puts the alignment crew in harm's way, takes an excessive amount of time, and prohibits obtaining precise measurements.
Thus, it would be desirable to provide a system, method, and assembly of aligning a motor to a pump, which can be performed while the motor does not require rotation, wherein improving alignment time and safety. It is to such a system, method and assembly to which the present invention is primarily directed.